Thats because the rest of the world need US dollars to buy fuel. We and as such we have the defacto world currency. But that is changing, every years green renewable energy makes up a higher proportion world energy and we use less carbon based fuel requireing out currency less and less. Secondly we are seeing other world powers build out the infrastructure for international banking denominated in other currencies to avoid the US banking regulation and sanctions. at some point the Dollar wont have the level of utility and dominance that to allows the US to do that sort of currency manipulation without consequences.